a-a a-b a-c aaa aab aac aad aak aar ab- aba abb abc abd abk abr ac- aca acb acc acd ack acr ad- ada adb adc add adk adr aka akb akc akd akk akr ar- ara arb arc ard ark arr baa bab bac bad bak bar bba bbb bbc bbd bbk bbr bca bcb bcc bcd bck bcr bda bdb bdc bdd bdk bdr bka bkb bkc bkk bkr bra brb brd brk brr c-- caa cab cac cad cak car cba cbb cbc cbd cbk cbr cca ccb ccc ccd cck ccr cda cdb cdc cdd cdk cdr cka ckb ckc ckd cra crb crc crd crk crr daa dab dac dad dak dar dba dbb dbc dbd dbk dbr dca dcb dcc dcd dck dcr dda ddb ddc ddd ddk ddr dka dkb dkc dkk dkr dra drb drc drd drk drr ka- kaa kab kac kad kak kar kba kbb kbc kbd kbk kbr kca kcb kcc kcd kck kcr kda kdb kdc kdk kdr kkb kkc kkk kkr kra krc krd krk krr ra- raa rab rac rad rak rar rba rbb rbc rbd rbk rbr rca rcb rcc rcd rcr rda rdb rdc rdd rdr rkb rkc rkk rra rrb rrc rrd rrk rrr